by Martin Holladay from Fine Homebuilding and Green Building Advisor
My first reaction was, “Product choices don’t matter very much.”, because it is ecologically more appropriate to renovate/reconstruct an existing house instead of adding the footprint and expenses of a new one.
Why do we build green homes? To reduce our carbon footprint (because we care about global climate change). To lower our energy costs To ensure that our homes are healthy.
My observations on the new-home market are not so rosy:
- New homes are often leaky.
- New homes are full of bump-outs and crazy roof designs.
- New homes are haphazardly insulated with fiberglass batts.
- New homes have leaky ducts in unconditioned attics.
What is more important than the choice of building material are these 5 principles to follow:
- Making sure your house is small
- Having a compact shape without bump-outs
- Orienting your house to the sun; making sure that 50% of your windows face south
- Creating a very tight thermal envelope and
- Adding plenty of insulation
However, there are 8 (relatively) new green building products:
- Zip sheathing (le revêtement mural intermédiaire Zip); It’s easier to put the air barrier at the sheathing layer than at the drywall layer.
Advantages: Resists moisture better than ordinary OSB; Once taped, the sheathing is as weatherproof as asphalt felt or Tyvek; It’s an easy way to get an airtight building envelope.
Disadvantages: It’s still OSB; It isn’t vapor-permeable.
- Air sealing tapes (bandes d’étanchéité);
European air sealing tapes manufactured by Pro Clima and Siga (Siga Wigluv) are available from:
475 High Performance Building Supply or Small Planet Workshop
They really work; i tested them and the Siga Wigluv tape proved to be the best.
- Triple-glazed windows (fenêtres à triple vitrage); they are very good event though they have 2 drawbacks: increased cost and lower SHGC (solar heat gain coefficient), because they insulate much better (consider that in winter the heat loss is bigger than the heat gain because the sun shines only 5or 6 hours per day…
Triple-glazed windows don’t just lower your energy bills; they also improve comfort. Because all cold surfaces drain radiant heat from your skin – if the inside window pane of a triple-glazed window is warm it won’t do that.
The best choice are Fiberglass windows are manufactured by:
Accurate Dorwin, Manitoba
Duxton Windows, Manitoba
Entreprises Marchand Portes et Fenêtres, Québec
Fibertec Windows, Ontario
Inline Fiberglass Windows, Ontario
Thermotech Fiberglass, Ontario
- Cellulose and mineral wool insulation (les fibres de cellulose et la laine minérale);
Cellulose has low embodied energy; and dense-packed cellulose reduces air leakage rates.
Mineral wool is denser and more fire resistant than fiberglass; mineral wool insulation can be used under non-load-bearing slabs.
- Roofing alternatives
- Recycled shingles, perhaps the “greenest” — of all roofing products are shingles made from recycled waste materials, such as plastic, rubber, or wood fiber. ($3.15/sqft meterial)
- Wood shingles from Maibec Industries ($6.65/sqft material)
- Slate and Clay tiles from Durable Slate ($9.20/sqft material)
- Metal roofing ($4.20/sqft material + $6.53 for labor)
- Recycled (tire) rubber roofing
- Ductless minisplits (les mini-thermopompes bibloc à haute efficacité sans conduits)
For energy-efficient homes in New England, using ductless minisplits for heating and cooling is now very common. Main manufacturer is Mitsubishi.
In some cases, only one or two minisplits can heat the entire house. They have low heat output ratings (10,000 to 12,000 Btuh) which are a good match for superinsulated homes.
They use electricity for fuel, which means: There is no combustion in the house; They work well with PV.
- Drainwater heat recovery devices (système de récupération de chaleur des eaux de drainage)
(Almost) Every new house should have one.
Difficult to install in single-story homes with slab foundations.
These devices work well for families that prefer showers – but not for families that prefer baths. These devices have no moving parts. They are very cost-effective in homes with electric-resistance water heaters. However, they are less cost-effective in homes with natural gas water heaters.
- PV systems (les systèmes photovoltaïques)
Prices keep dropping.
Since Québec has low electricity prices, this province is relatively unaffected by the PV revolution. This technology is deeply disruptive. My first PV module in 1980 cost me $8.33/watt.
The cost per watt is now under $1.
- LED lighting (appareils d’éclairage à diodes électroluminescentes – DEL)
The light quality is quite good.
These lamps are now affordable.
They are efficient and long-lived.
The price of these lamps will continue to drop.